Enhancing biological denitrification with adding sludge liquor of hydrolytic acidification pretreated by high-pressure homogenization

• Sewage sludge was effectively disintegrated by high-pressure homogenization (HPH).
• Sewage sludge pretreated by HPH was effectively hydrolyzed and acidified.
• Sludge liquor disintegrated and hydrolytically acidified was used as carbon source.
• TN removal increased by 51.0% with sludge liquor as denitrification carbon source.

In this study, high-pressure homogenization (HPH) pretreatment was chosen to enhance the hydrolytic acidification of excess sludge, and the sludge liquor obtained was added to a sequencing batch reactor (SBR) as external carbon source to enhance nitrogen removal. The results indicated that volatile fatty acids (VFAs), sludge disintegration degree (DDCOD) and NH4+-N increased with increasing the homogenization pressure. The maximum VFA concentration of 1936.0 mg/L was obtained after 3-day hydrolytic acidification with a HPH pretreatment of 40 MPa; acetic acid accounted for 54.4%, propionic acid for 18.3%, and other acids for 27.3% in the total VFAs. The sludge liquor of hydrolytic acidification with HPH disintegration (SLDHA) showed the best performance for wastewater denitrification, compared with the sludge liquor disintegrated alone or hydrolytically acidified alone. When the SLDHA was used as external denitrification carbon source, the total nitrogen removal increased by 51.0% compared to the control.